In wireless communication, signals are sent from a transmitter to a receiver using electromagnetic waves that emanate from an antenna. These electromagnetic waves may be sent equally in all directions or focused in one or more desired directions. When the electromagnetic waves are focused in a desired direction, the pattern formed by the electromagnetic wave is termed a “beam” or “beam pattern.” Hence, the production and/or application of such electromagnetic beams are typically referred to as “beamforming.”
Beamforming may provide a number of benefits such as greater range and/or coverage per unit of transmitted power, improved resistance to interference, increased immunity to the deleterious effects of multipath transmission signals, and so forth. Beamforming can be achieved (i) using a finely tuned vector modulator to drive each antenna element to thereby arbitrarily form beam shapes, (ii) by implementing full adaptive beam forming, and (iii) by connecting a transmit/receive signal processor to each port of a Butler matrix.
A traditional Butler matrix is a passive device that forms beams of a pre-determined size and shape that emanate from an antenna array that is connected to the Butler matrix. The Butler matrix includes a first set of ports that connect to the antenna array and a second set of ports that connect to multiple transmit/receive signal processors. The first set of ports are denoted as antenna ports, and the second set of ports are denoted as transmit/receive ports. The number of ports in each of the first and second sets may be considered to determine the order of the Butler matrix. While not required, Butler matrices typically have an order that is a power of two, such as 4, 8, 16, 32, and so forth. In a conventional wireless communications environment, every port of the set of antenna ports of a Butler matrix is connected to an antenna element, and every port of the set of transmit/receive ports of a Butler matrix is connected to a signal processor.
By way of example, a Butler matrix may have an order of 16. In this case, there are 16 transmit/receive signal processors connected to the 16 transmit/receive ports of the Butler matrix, and there are 16 antenna elements connected to the 16 antenna ports of the Butler matrix. In operation, multiple individual beams of a fixed size and shape emanate from the antenna array. Signals transmitted in and received from each of the respective 16 beams map to a predetermined one of the 16 signal processors on the 16 transmit/receive ports of the Butler matrix. Thus, there is a one-to-one correspondence between (i) each beam formed by the combination of the Butler matrix and the antenna array and (ii) each signal processor that is connected to the Butler matrix.
Accordingly, there is a need for schemes and/or techniques for improving the variety and versatility of wireless communication and beamforming options.